Universal Serial Bus (USB) is a peripheral interface for attaching a wide variety of computing devices, such as personal computers, digital telephone lines, monitors, modems, mice, printers, scanners, game controllers, keyboards, storage devices, and/or the like. The specifications defining USB (e.g., Intel et al., Universal Serial Bus Specification, Revision 1.0, January 1996; updated as Revision 1.1 in September 1998; and further updated as Revision 2.0 in April 2000; Universal Serial Bus 3.0 Specification, Revision 1.0, Jun. 6, 2011; Universal Serial Bus 3.1 Specification, Revision 1.0, Jul. 26, 2013; and subsequent updates and modifications—hereinafter collectively referred to as the “USB Specifications”, which term can include future modifications and revisions) are non-proprietary and are managed by an open industry organization known as the USB Forum. The USB Specifications establish basic criteria that must be met in order to comply with USB standards. One of ordinary skill in the art will recognize many terms herein from the USB Specifications. Those terms are used herein in a similar manner to their use in the USB Specifications, unless otherwise stated.
Under each of the USB Specifications, certain timing requirements are established that result in a maximum supported length for media that connects USB devices. For example, under the Universal Serial Bus 3.0 Specification, SuperSpeed connections are provided that use a 5 Gbps signaling rate. Though the specification does not mandate any particular maximum cable length, in practical terms the timing mandates and signaling techniques require a regular copper cable used for a SuperSpeed connection between a host and a device to be at most 3 meters long to properly support the SuperSpeed connection. Therefore, non-standard methods and apparatuses are needed to optionally allow for extension of a SuperSpeed USB device to a greater distance from the host to which it is coupled, such that SuperSpeed USB packets may be propagated between the host and the USB device, and such that SuperSpeed connections may be maintained between the host and the USB device even if the host and/or the device enter an idle or suspend state. Some examples of such methods and apparatuses are provided in commonly owned U.S. Pat. No. 8,868,792, issued Oct. 21, 2014, the entire disclosure of which is hereby incorporated herein for all purposes. Similar problems exist for the transmission of USB communication at other speeds (including but not limited to low speed, full speed, and high speed) between a host or hub and a USB device over a non-USB compliant extension medium.
The management of power delivery via USB, including the ability to negotiate voltage, current, and/or direction of power flow over the power conductor (Vbus), is described in the Universal Serial Bus Power Delivery Specification, Revision 1.0, including Errata through 11 Mar. 2014 (Version 1.3) (hereinafter “USB PD Specification 1.0”), available from the USB Implementers Forum at http://www.usb.org, the entirety of which is incorporated herein by reference for all purposes. The USB PD Specification 1.0 was updated to support the requirements of the USB Type-C specification and to incorporate additional changes, in the USB Power Delivery v2.0 Specification, published Aug. 11, 2014 (hereinafter “USB Power Delivery specification”, and collectively with the USB PD Specification 1.0 as “USB PD Specifications”) and available from the USB Implementers Forum at http://www.usb.org, the entirety of which is incorporated herein by reference for all purposes.
While the USB PD Specifications do describe the ability to manage power distribution over a USB topology, there is no discussion in the USB PD specifications regarding the management of power distribution in cases where a host or hub and a device are separated by a non-USB compliant extension medium.